Production of lubricating grease



l atented Aug. 28, 1951 UNITED STAT ES PAT 2,565,981 p PRODUCTION OF LUBRIGATIN G GREASE Arnold J Morway, ltahway, J II -Zela iiii; Cranford, and Gordon W. Duncan, Wstfield, N. J., assignois to Standard Oil D'evmp'ment Company, a corporation ofBelaware No Drawing. ApplicationjFebruary 18,1949;

' Serial No. 77,298

The present invention'relates to the production of lubricating greases and particularly to the production of greases which are thickened With metal soaps and also are modified by including therein certain acidogenic materials and/or the salts thereof.

Various suggestions have been made in the prior art for the improvementofhi'gh tempera ture properties and the modification of other properties of lubricating greases by mcdifyin'g" friction bearings as lubricants become available to maintain suchbearings. A number of sug'-' gestions have been made recently that thedr'op ping point or melting point of so'da base greases can be raised appreciably by incorporating therein a salt of a low' molecular weight'acid.

In the co-pending application of Mor'way, one of the present inventors, Serial No. 777,328; filed October 1, 1947, now Patent No. 2,468,099, there is disclosed a sup'erior'high temperature lubricating grease of the soda base typcprp'ared by incorporating into the grease composition a small amount, from about 0.1 to of an acid or acidogenic materm, preferably acrylic acid, methacrylic acid, crotonic acid, or the like; The application of Morway and Daniels, Serial No. 9,315, filed February 18, 1948, now Patent No. 2,468,098, also mentions the use of certain saturated acids such as glycolic or hydr'oxyacetic acid, alpha or beta hydroxy'buty'ric acid, acetoacetic acid; and the like. to the grease ingredients prior to saponification andthe sanponifying agent, usually sodium hydroxide, is added in sufficient quantity not only to form the soap with the fatty materials which" are present but also to neutralize or substantially neutralize and form a salt" with the acid or' acidogenic material.

Although the products described in the applications referred to above have desirable characteristics, it is desirable for several reasons to modify the methods of manufacture to overcome certain diificulties, Acrylic acid in particular is These acids are added" a highlytckic" material, and itshanjdlirig" is a tended with" same difli'culties and with so danger. n and a .eosuymatenar since airs ordinarily prepared from an ester. Thus; acrylic" acid may be obtairfjdby firstprepari'ng a"hy-" droxyfiitri'le'," e; g. CHiQI-L-CHZCN'; This nitrile dehyd'rates spontaneously toleave acrylonitri'le CI-Ii"=CHQN.1 The acryl ohitri'le' is esterified' by treating" it with af's'ilit able aliphatic alcohol, pref eraliilya"lower aliphatic" alcohol such as methyl;

= This ester, accordiri'g'to the" present invention; a'n'd related" analogcusesters'; may be used di=' rectly in lieu of" acrylic acid; in thes reparauoa of grease following" the general p'rdcedure' d scribed in the aforesaid application cf" Morway;

.Serial'No. 777,328. If it weredesired to -useacrylic acid" ra'ther than "the-"ester,- acid? would be derived ordinarilyfrom the same ester and its" cost would be considerably higher them;

that of the ester. Thispaaticularester has-the very important advantage of beingrelatively harmless to the humanskin whereas' the acid-is highly toxic and the simplicity of the present process, and "theeconomyof the ingredient rep resent-adistinct improvementover the process as the aforesaid application? Although various esters may be employedas noted above, the esters of row molecular weight monobasic acids; e: g-.,- acrylic, crotonic, ber izoic, and-the like arepr'eferred'because they are more readily available; muchless expensive andalsomay readily bereacted thedesired manner. The by-products, usually alcohols which are released upon neutral'izatiori', are readily disposed ofeither by eva oia-tmaor-by reeov iy in-the case of the lower aliphatic esters. Higher esters may be usedg'however, particularly where the alcohols which are-released upon treatment withalkali may be permitted toremainin the grease composition asplasticizersz- In -general; the O1 aliphaticesters of the-lower aliphatic acids are preferred; anathe- Gr to G4 esters of benzoicacid,- but other'esters-ofhigher chain length, up to 10 or'12 carbon atomsin-the alcohol radical; may beutilizedfin-some cases. a r

The esters of unsaturated acids such as acrylic acid, meth-ac'rylic acid, and creams acid; and

with ethyl anchor; cmcmom cm cHcNa 3 which the esters may be derived, or on which the esters may be based are numerous, but in general they should have not more than 6 or '7 carbon atoms, preferably 3 to 6 carbon atoms per molecule. Heterocyclic acid esters also may be used, for example, the lower aliphatic esters of furoic acid and the corresponding thio acids and their homologs.

Greases according to the present invention are prepared in much the same general way as those described in the aforesaid applications of Morway and Morway et al., except that equivalent molar quantities of ester are substituted for the acids. Thus, instead of using 0.1 to by weight of acid, based upon the total composition, a similar or slightly larger quantities, depending upon the molecular weight, of the ester may be used. The ester is added to the mineral oil and fatty material prior to saponification. Thereafter, saponifying agent, preferably sodium hydroxide, is added and the grease is cooked in the conventional manner to a temperature which may be as high as 500 F. or more, but usually is within the range of 250 to 450 F.

In this process the ester is hydrolyzed. In i order to prevent polymerization, when an acrylic, methacrylic or other polymerizable ester is used, a polymerization inhibitor should be used. Hydroquinone, thymol, phenyl naphthylamine and the polyalkylated phenols, e. g. 2,4,6 tri-tertiary butyl phenol, alkylated alkoxyphenols, and the like, are suitable. Aromatic amines may also be used. Small quantities of such inhibitors, e. g. 0.01 to l or 2% are quite adequate. By

proper choice of the polymerization inhibitor, the 1' grease may also be inhibited at the same time and for this purpose hydroquinone or phenyl a. or phenyl s naphthylamine are usually preferred. A combination may be used, since hydroquinone is a particularly preferred polymerization inhibitor whereas the phenyl naphthylamines are superior oxidation inhibitors.

Where the acid is used as in the above mentioned Morway application, water is evaporated whereas with the use of esters as in the present case an alcohol is given off, the type of alcohol depending upon the esterifying group. The following examples indicate the manner in which the ingredients may be combined and, in general,

they represent the replacement of acids with esters, with suitable control to prevent polymerization or other undesirable reactions. The process otherwise is quite similar to that described in the aforesaid Morway Patent No. 2,468,099.

Example I A grease composition was prepared of the following ingredients:

The methyl ester of acrylic acid (containing 1.0% of hydroquinone as a polymerization inhibitor) and approximately an equal quantity of mineral oil, were charged to a cold fire heated grease kettle equipped with means for adequate agitation. A 40% aqueous solution of sodium hydroxide was added and the ingredients were r, was next cooled, while stirring, to a temperature of 160 F. Agitation Was discontinued overnight and the next morning the cold grease was stirred to a smooth homogeneous product. It showed the following inspection:

Percent free alkalinity, as NaOH 0.53 Dropping point F 440 Worked penetration:

(60 strokes) mm./10 250 (6000 strokes) 280 (75000 strokes) 327 Water resistance (AN-G-lfi method) F 125 Water temperature, percent loss, none Mineral lubricating oil as in Example I 76.5

Preferred proportions of the ingredients are 10 to 20% of fatty material based on the total composition, although the weight of these ingredients may vary from as little as 5 to as much as 30%. The esters may be used in proportions of 0.1 or 0.2 up to about '7 or 8%, and the quantity of saponifying agent required should be enough to completely saponify the fatty materials and to completely or substantially completely hydrolyze th ester. A small excess of acidity or alkalinity may be permitted, however.

Conventional anti-oxidants such as phenyl alpha naphthylamine, phenyl beta naphthylamine, and the like, in quantities of about 0.1 to 1% may be used both as anti-oxidants and as polymerization inhibitors or they may be used with other polymerization inhibitors where the esters are polymerizable as the acrylic type esters are. Various other additives such as extreme pressure compounds, tackiness or stringiness agents, metal deactivators, corrosion inhibitors, and the like, may be employed as is well understood in the art. Unless the polymerization inhibitor is itself an anti-oxidant, an oxidation inhibitor should be added when cooking has been completed.

The lubricating oil is preferably a mineral oil of lubricating grade having a viscosity of 200 to 1,000 S. S. U. or more at F. Mineral oil should be used in the preparation of the grease. but a synthetic ester type lubricant may be prepared by using only a suflicient quantity of mineral oil to cook the soap-forming ingredients properly after which an ester oil such as di-2- ethylhexyl sebacate, and the like, may be used in lieu of the remainder of the mineral oil, as is also well understood in the art.

What is claimed is:

1. The process of preparing lubricating grease containing an alkali metal salt of a low molecular weight monocarboxylic acid which comprises the steps of adding 0.1 to 8% by weight, based on the final composition of a C1 to C4 aliphatic alcohol ester of said monocarboxylic acid to a hydrocarbon lubricating oil and 5 to 30% of a saponifiable fatty material, thereafter adding saponifying agent at an elevated temperature of 150 to 200 F., in quantity su-fficient to substantially hydrolyze and neutralize said ester and said fatty material, and finally cooking the ingredients to evaporate water and other volatile ingredients and to form a grease structure.

2. Process as in claim 1 wherein the ester is a C1 to C4 aliphatic ester of an unsaturated monocarboxylic aliphatic acid having 3 to 5 carbon atoms.

3. Process as in claim 1 wherein the ester is a C1 to C4 aliphatic ester of an acrylic acid.

4. Process according to claim 1 wherein the ester is a C1 to C4 aliphatic ester of crotonic acid.

5. Process according to claim 1 wherein the ester is a C1 to C4 aliphatic ester of glycolic acid.

6. Process according to claim 1 wherein the ester is a C1 to C4 aliphatic ester of methacrylic acid.

'7. Process as in claim 1 wherein said ester is a polymerizable ester of an unsaturated acid of 3 to 5 carbon atoms and a polymerization inhibitor is employed during said grease formation.

ARNOLD J. MORWAY. HOLLIS L. LELAND. GORDON W. DUNCAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,320,536 Pollack et al. June 1, 1943 2,455,892 Fraser Dec. 7, 1948 2,468,098 Morway et al Apr. 26, 1949 2,468,099 Morway Apr. 26, 1949 2,516,136 Morway et al. July 25, 1950 

1. THE PROCESS OF PREPARING LUBRICATING GREASE CONTAINING AN ALKALI METAL SALT OF A LOW MOLECULAR WEIGHT MONOCARBOXYLIC ACID WHICH COMPRISES THE STEPS OF ADDING 0.1 TO 8% BY WEIGHT, BASED ON THE FINAL COMPOSITION OF A C1 AND C4 ALIPHATIC ALCOHOL ESTER OF SAID MONOCARBOXYLIC ACID TO A HYDROCARBON LUBRICATING OIL AND 5 TO 30% OF A SAPONIFIABLE FATTY MATERIAL, THEREAFTER ADDING SAPONIFYING AGENT AT AN ELEVATED TEMPERATURE OF 150 TO 200* F., IN QUANTITY SUFFICIENT TO SUBSTANTIALLY HYDROLYZE AND NEUTRALIZE SAID ESTER AND SAID FATTY MATERIAL, AND FINALLY COOKING THE INGREDIENTS TO EVAPORATE WATER AND OTHER VOLATILE INGREDIENTS AND TO FORM A GREASE STRUCTURE. 